Characters in keys

Any valid Unicode character can appear in an OSM key but usually
only lower case latin letters (a-z) and the underscore (_) are
used. The colon (:) is often used as a separator character. This
report categorizes all keys according to the characters they use.

Statistics overview

Only latin lowercase letters (a to z) and underscore (_), first and last characters are letters.

B

2227

56.31%

Like A but with one or more colons (:) inside.

C

440

11.13%

Like B but with uppercase latin letters or letters from other alphabets.

D

1

0.03%

At least one whitespace character (space, tab, new line, carriage return, or from other alphabets).

E

14

0.35%

Contains possibly problematic characters =+/&<>;'"?%#@\,.

F

54

1.37%

Everything else.

3955

100%

Total

Plain keys

Keys containing only lowercase latin letters (a to z) and the
underscore (_). First and last
characters must be letters. Most simple keys should fall into
this category.

Keys with colon

Keys that have one or more colon (:) characters inside in addition to the
letters (a to z) and underscores (_). The colon is often used as a hierarchy
separator character.

Keys with uppercase letters or letters from other scripts

Lowercase letters from the latin script are usually
preferred for keys, but sometimes uppercase letters are used
(for instance for known abbreviations) or letters from other
scripts (for instance for keys only relevant to an area where
that script is used predominantly).

Keys with whitespace

Keys that contain whitespace characters such as space, tab,
new line, carriage return, or whitespace characters from other
alphabets. Whitespace in keys can be confusing, especially at
the beginning or end of the key, because they are invisible.
Generally the whitespace should be removed or the underscore
(_) used instead.

Keys with possibly problematic characters

Keys that contain possibly problematic characters: =+/&<>;'"?%#@\, or control
characters. These characters can be problematic, because they
are used to quote strings in different programming languages or
have special meanings in XML, HTML, URLs, and other places. The
equal sign is used often as separator between tag keys and
values. Keys that appear in this list are not necessarily wrong
though. But in many cases they are just results of some error
and should be fixed.